[1] The present disclosure relates to the field of photonic networks and, more
particularly, to the networks that receive optical signals as input and provide adaptive channelized optical energy or signals as output.
BACKGROUND
[2] With the continued rapid development and availability of the Internet - video
conferencing, real-time gaming, IPTV high-bandwidth applications continue to emerge leading to a higher demand for the network bandwidth. Optical fibermaterial provides huge bandwidth advantage and techniques required to fulfil large bandwidth requirements are available in market.
[3] However, the available techniques such as dispersion compensating fiber
(DCF), decision feedback equalizer(DFE), coherent detection (CD), advanced modulation
formats such as M-ary phase shift keying(M-PSK) and M-ary quadrature amplitude
modulation (M-QAM) suffer from multiple limitations like limited transmission rate,
insertion loss, working on higher data rates leading to high power consumption and heating
issues. Also, quadrature phase shift keying does not perform efficiently for short distances
and requires using a long cyclic prefix that adds unnecessary overhead on the network.
[4] Thus, there is a need to provide a solution to obtain high performance photonic
transmission so to meet the ever evolving bandwidth needs. The solution provides a technique for effective bandwidth utilization of the network so to avoid wastage of valuable network resources and mitigates the channel impairments to obtain enhanced network performance.
OBJECTS OF THE PRESENT DISCLOSURE
[5] A general object of the present disclosure is to manage bandwidth resource
pool of a network by adjusting parameters such as cyclic prefix, number of subcarriers, and
modulator order at a transmitter unit in real time.
[6] Another object of the present disclosure is to provide a coherent detection for
optical orthogonal frequency division multiplexing (OOFDM) so as to improve efficient
spectral efficiency of the network with improved communication data rate and detection
performance.

SUMMARY
[7] The present disclosure relates to systems and methods for receiving optical
signals as input and providing adaptive channelized optical energy or signals as output in a
photonic network.
[8] An aspect of the present disclosure relates to a device for improving spectral
efficiency of a channel in a photonic network, said device comprising: a receiver to
continuously monitor the channel to determine a signal to noise ratio (SNR) information; and
a transmitter to receive the SNR information and based on the SNR information adjusting a
combination of one or more parameters of the channel so as to optimize bandwidth utilization
of the channel.
[9] According to an embodiment, the adjusted parameters of the channel are at
least one or more of a cyclic prefix length, a number of subcarriers and a modulation order.
[10] According to an embodiment, the cyclic prefix length is increased upon the
receiver conveying unsatisfactory SNR information.
[11] According to an embodiment, the cyclic prefix length is decreased upon the
receiver conveying satisfactory SNR information.
[12] According to an embodiment, the receiver continuously monitors and delivers
the SNR information of the channel to the transmitter via a separate feedback channel.
[13] Another aspect of the present disclosure relates to a method for improving
spectral efficiency of a channel in a photonic network, said method comprising: a receiver to
continuously monitor the channel to determine a signal to noise ratio (SNR) information,
where the SNR information is transmitted to a transmitter; and the transmitter to adjust a
combination of one or more parameters of the channel based on the received SNR
information.
[14] According to an embodiment, an adaptive subcarrier allocation strategy is
used to allocate the subcarriers based on real time user requirements and the channel
conditions.
[15] According to an embodiment, the modulation order refers to selection of M
combinations of amplitude and phase shifts for a M-ary Quadrature amplitude modulation
(M-ary QAM).
[16] According to an embodiment, the SNR information at the receiver is detected
through coherent detection.
[17] Various objects, features, aspects and advantages of the inventive subject
matter will become more apparent from the following detailed description of preferred

embodiments, along with the accompanying drawing figures in which like numerals represent like components.
BRIEF DESCRIPTION OF DRAWINGS
[18] The accompanying drawings are included to provide a further understanding
of the present disclosure and are incorporated in and constitute a part of this specification.
The drawings illustrate exemplary embodiments of the present disclosure and, together with
the description, serve to explain the principles of the present disclosure. The diagrams are for
illustration only, which thus is not a limitation of the present disclosure.
[19] FIG. 1 illustrates proposed implementation architecture of a photonic device in a
photonic network for an optical transmission, 100.
[20] FIG. 2 illustrates an exemplary module diagram for the proposed
implementation architecture of the disclosure for the optical transmission, 200.
DETAILED DESCRIPTION
[21] The following is a detailed description of embodiments of the disclosure
depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[22] In the following description, numerous specific details are set forth in order to
provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.
[23] Embodiments of the present invention include various steps, which will be
described below. The steps may be performed by hardware components or may be embodied in machine-executable instructions, which may be used to cause a general-purpose or special-purpose processor programmed with the instructions to perform the steps. Alternatively, steps may be performed by a combination of hardware, software, and firmware and/or by human operators.
[24] Various methods described herein may be practiced by combining one or more
machine-readable storage media containing the code according to the present invention with appropriate standard computer hardware to execute the code contained therein. An apparatus

for practicing various embodiments of the present invention may involve one or more
computers (or one or more processors within a single computer) and storage systems
containing or having network access to computer program(s) coded in accordance with
various methods described herein, and the method steps of the invention could be
accomplished by modules, routines, subroutines, or subparts of a computer program product.
[25] If the specification states a component or feature "may", "can", "could", or
"might" be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[26] As used in the description herein and throughout the claims that follow, the
meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.
[27] Exemplary embodiments will now be described more fully hereinafter with
reference to the accompanying drawings, in which exemplary embodiments are shown. These exemplary embodiments are provided only for illustrative purposes and so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those of ordinary skill in the art. The invention disclosed may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Various modifications will be readily apparent to persons skilled in the art. The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Moreover, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure). Also, the terminology and phraseology used is for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present invention is to be accorded the widest scope encompassing numerous alternatives, modifications and equivalents consistent with the principles and features disclosed. For purpose of clarity, details relating to technical material that is known in the technical fields related to the invention have not been described in detail so as not to unnecessarily obscure the present invention.
[28] Thus, for example, it will be appreciated by those of ordinary skill in the art
that the diagrams, schematics, illustrations, and the like represent conceptual views or

processes illustrating systems and methods embodying this invention. The functions of the various elements shown in the figures may be provided through the use of dedicated hardware as well as hardware capable of executing associated software. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the entity implementing this invention. Those of ordinary skill in the art further understand that the exemplary hardware, software, processes, methods, and/or operating systems described herein are for illustrative purposes and, thus, are not intended to be limited to any particular named element.
[29] Embodiments of the present invention may be provided as a computer
program product, which may include a machine-readable storage medium tangibly embodying thereon instructions, which may be used to program a computer (or other electronic devices) to perform a process. The term “machine-readable storage medium” or “computer-readable storage medium” includes, but is not limited to, fixed (hard) drives, magnetic tape, floppy diskettes, optical disks, compact disc read-only memories (CD-ROMs), and magneto-optical disks, semiconductor memories, such as ROMs, PROMs, random access memories (RAMs), programmable read-only memories (PROMs), erasable PROMs (EPROMs), electrically erasable PROMs (EEPROMs), flash memory, magnetic or optical cards, or other type of media/machine-readable medium suitable for storing electronic instructions (e.g., computer programming code, such as software or firmware).A machine-readable medium may include a non-transitory medium in which data may be stored and that does not include carrier waves and/or transitory electronic signals propagating wirelessly or over wired connections. Examples of a non-transitory medium may include, but are not limited to, a magnetic disk or tape, optical storage media such as compact disk (CD) or digital versatile disk (DVD), flash memory, memory or memory devices. A computer-program product may include code and/or machine-executable instructions that may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.
6

[30] Furthermore, embodiments may be implemented by hardware, software,
firmware, middleware, microcode, hardware description languages, or any combination
thereof. When implemented in software, firmware, middleware or microcode, the program
code or code segments to perform the necessary tasks (e.g., a computer-program product)
may be stored in a machine-readable medium. A processor(s) may perform the necessary
tasks.
[31] Systems depicted in some of the figures may be provided in various
configurations. In some embodiments, the systems may be configured as a distributed system
where one or more components of the system are distributed across one or more networks in
a cloud computing system.
[32] Each of the appended claims defines a separate invention, which for
infringement purposes is recognized as including equivalents to the various elements or
limitations specified in the claims. Depending on the context, all references below to the
"invention" may in some cases refer to certain specific embodiments only. In other cases it
will be recognized that references to the "invention" will refer to subject matter recited in one
or more, but not necessarily all, of the claims.
[33] All methods described herein may be performed in any suitable order unless
otherwise indicated herein or otherwise clearly contradicted by context. The use of any and
all examples, or exemplary language (e.g., “such as”) provided with respect to certain
embodiments herein is intended merely to better illuminate the invention and does not pose a
limitation on the scope of the invention otherwise claimed. No language in the specification
should be construed as indicating any non-claimed element essential to the practice of the
invention.
[34] Various terms as used herein are shown below. To the extent a term used in a
claim is not defined below, it should be given the broadest definition persons in the pertinent
art have given that term as reflected in printed publications and issued patents at the time of
filing.
[35] The present disclosure relates to systems and methods for receiving optical
signals as input and providing adaptive channelized optical energy or signals as output in a
photonic network.
[36] An aspect of the present disclosure relates to a device for improving spectral
efficiency of a channel in a photonic network, said device comprising: a receiver to
continuously monitor the channel to determine a signal to noise ratio (SNR) information; and
a transmitter to receive the SNR information and based on the SNR information adjusting a
7

combination of one or more parameters of the channel so as to optimize bandwidth utilization
of the channel.
[37] According to an embodiment, the adjusted parameters of the channel are at
least one or more of a cyclic prefix length, a number of subcarriers and a modulation order.
[38] According to an embodiment, the cyclic prefix length is increased upon the
receiver conveying unsatisfactory SNR information.
[39] According to an embodiment, the cyclic prefix length is decreased upon the
receiver conveying satisfactory SNR information.
[40] According to an embodiment, the receiver continuously monitors and delivers
the SNR information of the channel to the transmitter via a separate feedback channel.
[41] Another aspect of the present disclosure relates to a method for improving
spectral efficiency of a channel in a photonic network, said method comprising: a receiver to
continuously monitor the channel to determine a signal to noise ratio (SNR) information,
where the SNR information is transmitted to a transmitter; and the transmitter to adjust a
combination of one or more parameters of the channel based on the received SNR
information.
[42] According to an embodiment, an adaptive subcarrier allocation strategy is
used to allocate the subcarriers based on real time user requirements and the channel
conditions.
[43] According to an embodiment, the modulation order refers to selection of M
combinations of amplitude and phase shifts for a M-ary Quadrature amplitude modulation
(M-ary QAM).
[44] According to an embodiment, the SNR information at the receiver is detected
through coherent detection.
[45] The technical benefits achieved by the implementation of various
embodiments of the present disclosure are as recited below:
[46] The present invention solves the above recited and other available technical
problems by adjusting the following parameters of the channel such as cyclic prefix, number
of subcarriers and modulation order in real time at the transmitter unit, based on SNR
information as received from the receiver.
[47] FIG. 1 illustrates proposed implementation architecture of a photonic device in a
photonic network for an optical transmission, 100.
[48] In an embodiment of the disclosure, the photonic network has the following
functional blocks: an OFDM modulator unit 102, an electrical to optical conversion unit 104,
8

a fiber link 106, an optical to electrical conversion unit 108, and an OFDM demodulation unit
110.
[49] In an aspect, a smart processing unit at the OFDM modulator unit 102
(transmitter) is present that manages bandwidth resource pool of the channel by adjusting
parameters such as scalable cyclic prefix and number of sub-carriers.
[50] In an aspect, the smart processing unit at the OFDM modulator unit 102 can
be a function or a set of instructions running on a processor.
[51] In an aspect, the smart processing unit can perform real time scalability of the
parameters such as the cyclic prefix length and the number of subcarriers.
[52] In an aspect, the smart processing unit uses real time information obtained
from the receiver regarding the signal to noise ratio (SNR) for selecting the cyclic prefix
length in real time.
[53] In an aspect, when the channel conditions are unsatisfactory as reflected by the
received SNR, the cyclic prefix length can be increased and for satisfactory channel
conditions the cyclic prefix length can be decreased so as to yield effective bandwidth
utilization.
[54] In an aspect, the device can use an adaptive subcarrier allocation strategy
where allocations of the subcarriers are done according to real time user requirement and the
prevalent channel conditions.
[55] In an aspect, using the subcarrier allocation strategy facilitates maximizing
data rate of the channel and better allocation of the channel among the users for achieving
improved BER performance.
[56] In an aspect, the OFDM modulator unit can mitigate inter symbol interference
by using a guard interval.
[57] In an aspect, requirement of equalizers in the OFDM modulator can be
reduced by providing an efficient design of the Optical Orthogonal Frequency Division
Multiplexing (OOFDM) system.
[58] In an aspect, increasing the number of subcarriers can be effective against
dispersion and facilitates improving the bandwidth utilization of the channel.
[59] In an aspect, for fixed sampling frequency - increase in the number of
subcarriers decreases frequency spacing between the subcarriers which in turn reduces walk
off induced by dispersion leading to occurrence of distortions in reduced percentage of the
subcarriers.
9

[60] In an aspect, the inter symbol interference can be reduced by selecting a
sufficiently large number of the subcarriers which make an OFDM symbol period considerably larger than dispersed pulse. Increased number of the subcarriers within one symbol enhances tolerance towards dispersion and improves transmission performance of the channel. However, increase in the number of subcarriers beyond a limit may also degrade the network performance as increased number of the subcarriers reduces frequency spacing between the adjacent subcarriers.
[61] In an aspect, due to the reduced frequency spacing - fiber non-linearities
affects orthogonality, leading to occurrence of inter carrier interference. The transmission parameters at the receiver are selected for maximizing the data rate and fairness of distribution of the channel among the users for achieving better bit error rate (BER) performance over reduced cyclic prefix coherently modulated optical orthogonal frequency division multiplexed (RCP-CO-OOFDM) transmission compensated for chromatic dispersion, non-linearities and phase drift.
[62] In an aspect, the adaptive subcarrier allocation strategy is designed based on
the data rate expectation of the user and the present channel conditions. The implemented strategy avoids the user with sufficient channel conditions to sweep out the entire subcarriers. As per the strategy the users with insufficient channel conditions are allocated a minimum of the subcarriers as per the data rate demand.
[63] In an aspect, the fast data rate is divided into multiple parallel paths to perform
“serial to parallel” conversion. The count of the parallel paths is equal to number of the sub-carriers.
[64] In an aspect, selection of the appropriate modulation order is based on the
instantaneously received SNR information from the receiver. The converted data is mapped to a modulation format.
[65] In an aspect, the modulation order can be a Mary-Quadrature amplitude
modulation or any other suitable form of modulation.
[66] In an aspect, the obtained modulated information is passed through an inverse
fast Fourier transform (iFFT) unit, a cyclic prefix (CP) addition unit, and is then shaped for transmission.
[67] In an aspect, to convert a digital signal to analog signal - Digital-to-signal
converters (DACs) are used.
10

[68] In an embodiment, the electrical to optical conversion unit 104 obtains an
optical signal by modulating CW source (tunable laser locked at 1550 nm) using nested LiNbO3 Mach-Zehnder modulator (MZM).
[69] In an aspect, an obtained optical signal is passed through four 80-km spans of
amplified single mode optical fiber link, 106.
[70] In an embodiment, the optical to electrical conversion unit 108 receives the
optical signal from the optical conversion unit 104 and converts it to an electrical signal with the coherent detection.
[71] In an aspect, down conversion of the signal is performed by using a local-
oscillator (LO) laser and balanced optical receiver(s), followed by the photo detector. The LO is locked to carrier phase after detection.
[72] In an aspect, a smart processing unit at the OFDM demodulation unit 110
(receiver) is present that evaluates the signal to noise ratio (SNR) information of the channel. This information is sent to the smart processing unit of the OFDM modulator unit 102 (transmitter) to calculate the cyclic prefix length, number of subcarriers and modulation order in real time.
[73] In an aspect, the smart processing unit at the OFDM demodulation unit 110
can be a function or a set of instructions running on a processor.
[74] In an aspect, the received electrical signal from the transmitter is processed
through a chain consisting of parallel to serial conversion, followed by real time equalization to compensate non-linearities, cyclic prefix (CP) stripping, fast Fourier transform (FFT) and demodulation to recover the final data.
[75] In an aspect, the device can integrate combined advantages of coherent
detection in the OOFDM and real time signal processing at the transmitter and the receiver end to decide suitable length of the cyclic prefix, the number of subcarriers and the modulation order.
[76] In an aspect, the device facilitates to provide better spectral efficiency with
improved communication data rate and detection performance.
[77] FIG. 2 illustrates an exemplary module diagram for the proposed
implementation architecture of the disclosure for the optical transmission, 200.
[78] At block 202, an input data is fetched at the transmitter. The initial working of
the transmitter present at the photonic device requires performing real time choice of parameters such as cyclic prefix duration, number of sub-carriers and modulation order by the transmitter.
11

[79] In an aspect, in order to make the photonic device functional the input data at
the transmitter is tuned on a set of training data. The training data is selected by fixing the value of cyclic prefix duration to be ¼ of training symbol duration so to avoid the inter-symbol interference. The number of the subcarriers is set equal of size of fast Fourier transform (FFT) and the modulation order is set to 64 (64-QAM). Upon the training data being sent by the transmitter, the receiver performs the coherent detection to analyse the channel and determine the SNR. The SNR information is communicated back as feedback to the receiver via the feedback channel.
[80] In an aspect the feedback channel can be a virtual or a wireless channel.
[81] In an aspect, the transmitter obtains the feedback and updates the parameters
for performance enhancement of the network. Subsequently the transmission of actual data
begins and real time feedback continues from the receiver to the transmitter.
[82] At block 204, based on the received input data, the OFDM modulation
transmitter unit 102 adjusts the channel parameters such as the cyclic prefix length, number of the subcarriers and the modulation order.
[83] At block 206, the electrical to optical conversion unit converts the electrical
signal to optical signal.
[84] At block 208, the converted optical signal is passed via the fiber link 106 to
the optical to electrical conversion block, where the signal is converted back to electrical form.
[85] At block 210, the receiver module at the OFDM demodulation unit analyses
the channel for various conditions and calculates the SNR information of the channel.The determined SNR information is passed as feedback to the block 202. This input data is used by the transmitter to adjust the multiple channel parameters for obtaining spectral efficiency of the channel.
[86] In an aspect, Cyclic prefix (CP) is an important characteristic of the optical
OFDM system to combat inter-adjacent-symbol interference (ISI).
[87] Thus the present disclosure aims to integrate the merits of the coherent
detection in OOFDM and real time signal processing at the transmitter and the receiver end to decide suitable length of the cyclic prefix, number of subcarriers and the modulation order, thus providing improved spectral efficiency with improved communication data rate and the detection performance.
[88] While the foregoing describes various embodiments of the invention, other
and further embodiments of the invention may be devised without departing from the basic
12

scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
ADVANTAGES OF THE PRESENT DISCLOSURE
[89] The present disclosure provides coherent detection of the channel for
improving the receiver sensitivity and data recovery.
[90] The present disclosure provides a function to track the transmitter phase for
extracting exact information of phase, frequency and amplitude.
[91] The present disclosure provides a device that is based on OOFDM and is
spectrally efficient to meet extensive data rate requirements.
[92] The present disclosure provides a function for balancing chromatic dispersion
and polarization mode dispersion thereby reducing cost of using dispersion compensators in
an optical domain.
[93] The present disclosure provides a device that incorporates scalability of cyclic
prefix and number of subcarriers in real time selection by using the smart processing unit at
transmitter.
[94] The present disclosure provides a function for real time adapting of length of
the cyclic prefix to ensure high spectral efficiency by avoiding unnecessary overhead and
robustness against inter-carrier and inter-symbol interference, and adaptability to channel
conditions.
[95] The present disclosure provides a function for the sub-carriers being selected
in the real time based on the channel conditions and the user demand so as to ensure
appropriate fulfilment of demands of present digital society.
[96] The present disclosure provides a function to adjust modulation format at the
transmitter based on the received SNR information so to enhance spectral efficiency of the
channel and to maintain low bit error rate (BER).

We Claim:

A device for improving spectral efficiency of a channel in a photonic network,
said device comprising :
a receiver to continuously monitor the channel to determine a signal to noise ratio (SNR) information; and
a transmitter to receive the SNR information and based on the SNR information adjusting a combination of one or more parameters of the channel so as to optimize bandwidth utilization of the channel.
2. The device as claimed in claim 1, wherein the adjusted parameters of the channel are at least one or more of a cyclic prefix length, a number of subcarriers and a modulation order.
3. The device as claimed in claim 1, wherein the cyclic prefix length is increased upon the receiver conveying unsatisfactory SNR information.
4. The device as claimed in claim 1, wherein the cyclic prefix length is decreased upon the receiver conveying satisfactory SNR information.
5. The device as claimed in claim 1, wherein the receiver continuously monitors and delivers the SNR information of the channel to the transmitter via a separate feedback channel.
6. A method for improving spectral efficiency of a channel in a photonic network, said method comprising :
a receiver to continuously monitor the channel to determine a signal to noise ratio (SNR) information, where the SNR information is transmitted to a transmitter; and
the transmitter to adjust a combination of one or more parameters of the channel based on the received SNR information.
7. The method as claimed in claim 1, wherein the adjusted parameters of the channel are atleast one or more of a cyclic prefix length, a number of subcarriers and a modulation order.
8. The method as claimed in claim 7, wherein an adaptive subcarrier allocation strategy is used to allocate the subcarriers based on real time user requirements and the channel conditions.

9. The method as claimed in claim 7, wherein the modulation order refers to selection of M combinations of amplitude and phase shifts for a M-ary Quadrature amplitude modulation (M-ary QAM).
10. The method as claimed in claim 1, wherein the SNR information at the receiver is detected through coherent detection.